1. Field of the Invention
This invention relates to high corrosion-resistant electromagnetic stainless steels having not only an excellent corrosion resistance but also good soft magnetic properties and workability, particularly cold forgeability, and more particularly to high corrosion-resistant electromagnetic stainless steels suitable for use in a housing for an electronically controlled fuel injection system for automobiles, an electromagnetic valve for water requiring corrosion resistance and the like.
2. Related Art Statement
The demand for recently developed electronically controlled fuel, injection systems has rapidly increased with the rapid advance of car electronics.
In this connection, pure iron, silicon steel containing 3% of Si, 13Cr-Si, or Al series ferritic stainless steel have hitherto been used as a material for such an electronically controlled fuel injection system.
Lately, dust pollution from road damage of based on the use of spike tires in the winter season is getting more and more aggravated, so that the use of spike tires tends to be prohibited in vehicles other than emergency vehicles. As a result, it is attempted to improve snow-removing or snow melting conditions, and a great amount of a snow melting agent such as magnesium chloride, calcium chloride or the like is used.
Since such a chloride is very strongly corrosive, however, it is required to have a higher corrosion resistance in a material for various parts of the automobile running on roads scattered with the snow melting agent. This is also true of the electronically controlled fuel injection system for automobiles. In this connection, sufficiently satisfactory corrosion resistance could not be expected in the aforementioned conventional steels.
To this end, it is attempted to improve the corrosion resistance by plating the above part or coating the part with a resin as a countermeasure.
However, rust occurs due to the defects such as pinholes or the like in case of the plating or due to the gap between resin and magnetic material in case of the resin coating, and consequently satisfactory corrosion resistance is not obtained and also the cost rises.
As a material having high corrosion resistance, there are austenitic stainless steels such as SUS 304 (18Cr-8Ni), SUS 316 (18Cr-12Ni-2Mo) and the like. However, these alloys are non-magnetic, so that they cannot be used as a material for the housing of electronically controlled fuel injection system for automobiles.
Since a practical material having a level of corrosion resistance equal to that of SUS 304 and good soft magnetic, properties does not exist at the present, there is a strong demand to develop such a material.
Moreover, the material for the housing of the electronically controlled fuel injection system for automobiles is also required to have a good cold forgeability in addition to the above properties because it is advantageous to conduct cutting, drilling and cold forging in order to cheaply enable mass production.